Study On Microstructure And Energy Saving Characteristics Of Rock Wool Board Used For Building External Wall Insulation System

In recent years,energy saving and emission reduction are getting more and more attention with the economic development,rock wool,as a kind of excellent thermal insulation material,is widely used in exterior wall insulation system.At the same time,how to further enhance the performance index of the rock wool board,improve their position in the durability of exterior wall in the complex environment and predict the safety and reliability during the service,has become the new thermal insulation material used in building exterior wall retaining structure system the development direction and key problems to be solved.Due to the particularity of materials,traditional test methods can not solve these problems effectively.In this study,Geodict software was used to detect the microstructure of rock wool board used for building exterior walls,and its structural characteristics were analyzed by computer.On this basis,the corresponding relation between the microstrmcture characteristics and the energy saving properties of rock wool board are established.Combined with the traditional laboratory test method,the change trend of the energy saving property of rock wool board in the environment of building exterior wall is explored.The main research contents and results are as follows:(1)The chemical composition and physical parameters of rock wool board were analyzed and the micro-structure of rock wool board was quantified.It is found that the acidity coefficient of the rock wool board can ensure that the material skeleton is relatively stable during the erosion process.The distribution of individual fiber diameter distribution in the plate is Gauss distribution.(2)The Geodict software was used to establish the true model and simplified model which can reflect the geometric characteristics of the rock wool board.The thermal conductivity of the individual fiber was calculated by the software on the basis of the traditional test results.The test results show that the thermal conductivity of rock wool single fiber is 1.25W/(m·K).This result is very close to the thermal conductivity of artificial diabase glass,which proved that the calculation results are reliable.The experiment provides a new way for measuring the thermal conductivity of single fiber.(3)Using simplified model to study the influence of density change and individual fiber diameter change on the rock wool board thermal conductivity.The reliability of the simulation experiment method was demonstrated by the heat flow meter method.It is found that the thermal conductivity of the rock wool board is positively correlated with the density linearity.However,the thermal conductivity is positively correlated with the rock wool single fiber diameter non-linearity and it is tends to be fixed.When rock wool density is between 140 and 200kg/m3,Geodict software can predict thermal conductivity of rock wool board accurately.When the rock wool density is less than 180kg/m3,the thermal conductivity of rock wool board can be guaranteed.The thermal insulation performance of rock wool board will be improved if the diameter of rock wool single fiber is less than 5?m.The research results provide the key technical ideas for the optimization measures of the mesoscopic structure of rock wool board,which are widely used in building envelope energy conservation.(4)The influence of solution corrosion on thermal conductivity of rock wool board was studied by immersing rock wool boards in acid solutions,water and alkali solutions.It is found that the erosion effect of three solutions on rock wool boards can not be ignored.The influence of corrosion on material is the largest in the early stage of corrosion and the corrosivity of alkaline solution is highest.(5)The relationship between pore filling rate and the thermal conductivity of rock wool board was calculated by series thermal resistance method and Geodict software.It is found that the thermal conductivity of the rock wool board is within 0.04W/(m·K)when the pore filling rate of the cotton plate is less than 20%.When rock filling rate is no less than 60%,the thermal conductivity of rock wool board increases quickly.When the pore filling rate of the rock wool board is greater than 90%,the thermal conductivity of the plate increases dramatically.As a result,it is necessary to ensure that the pore filling rate of rock wool board is less than 20%and emergency measures should be taken when the pore filling rate of rock wool board is greater than 90%.